Sign readable at speed

Abstract

A sign having an array of elements each comprising a first lens, a second lens and an optical object in registry with the first and second lenses such that the virtual image of the optical object formed in the second lens lies in the focal surface of the first lens. The optical objects are a representation of the information which the sign is to present. The image of the optical objects seen by a viewer moving past the sign appears to be stationary with respect to the viewer.

I claim: 
     
       1. A sign for presenting information to an observer moving with respect thereto, charactrised in that the sign comprises a plurality of elements linearly disposed with respect to one another, each of which elements comprises first and second coaxial lenses and an optical object consisting of a representation of the information which the sign is to present and in registry with said first and second lenses, the optical object of each element being substantially identical and said first lens constituting the external surface of the sign, wherein the virtual image of the optical object formed by said second lens of each element lies in the focal surface of the first lens of the element such that light rays emanating from any point on the optical object through the second lens emerge in a substantially parallel manner from the first lens. 
     
     
       2. A sign as claimed in claim 1 wherein the fist lens of each element is an aspheric hexagonal lens. 
     
     
       3. A sign as claimed in claim 2 wherein the second lens of each element is a plano-concave lens, the plane surface of which is most remote from the first lens of the element and wherein the optical object lies directly on said plane surface. 
     
     
       4. A sign as claimed in claim 2 wherein the second lens of each element is a fresnel lens of negative power and having fresnel grooves formed in its surface nearer to the first lens of the element and wherein the optical object of each element is mounted at a fixed distance from said second lens in the direction away from said first lens. 
     
     
       5. A sign as claimed in claim 2 wherein the first lens of each element is partially covered by an opaque diaphragm defining an aperture coaxial with the lens. 
     
     
       6. A sign as claimed in claim 5 wherein each aperture is a hexagonal aperture which is displaced by 30° with respect to the first lens, about their common axis. 
     
     
       7. A sign as claimed in claim 1 wherein the first lens of each element is a fresnel lens. 
     
     
       8. A sign as claimed in claim 1 wherein the sign includes a light source by means of which the optical objects are illuminated. 
     
     
       9. A sign as claimed in claim 1 wherein the elements comprise a tessellated array. 
     
     
       10. A sign as claimed in claim 9 wherein opaque partitions are located between adjacent elements.